Magnetically controlled delivery of subterranean fluid additives for use in subterranean applications

ABSTRACT

Various compositions are provided herein that include a composition that includes a well bore treatment fluid and a magnetically-sensitive component that includes a subterranean fluid additive. In some instances, the magnetically-sensitive component may be a ferrogel. In some instances, the ferrogel may include a polymer matrix and a magnetic species.

BACKGROUND

The present invention relates to subterranean treatment operations, andmore particularly, to providing controlled delivery of subterraneanfluid additives to a well bore treatment fluid and/or a surroundingsubterranean environment using intelligent materials that respond to amagnetic stimulus to release subterranean fluid additives downhole in asubterranean environment.

Natural resources such as oil and gas located in a subterraneanformation can be recovered by drilling a well bore in the subterraneanformation, typically while circulating a drilling fluid in the wellbore. After the well bore is drilled, a string of pipe, e.g., casing,can be run in the well bore. The drilling fluid is then circulateddownwardly through the interior of the pipe and upwardly through theannulus between the exterior of the pipe and the walls of the well bore,although other methodologies are known in the art.

Hydraulic cement compositions are commonly employed in the drilling,completion and repair of oil and gas wells. For example, hydrauliccement compositions are utilized in primary cementing operations wherebystrings of pipe such as casing or liners are cemented into well bores.In performing primary cementing, a hydraulic cement composition ispumped into the annular space between the walls of a well bore and theexterior surfaces of a pipe string disposed therein. The cementcomposition is allowed to set in the annular space, thus forming anannular sheath of hardened substantially impermeable cement. This cementsheath physically supports and positions the pipe string relative to thewalls of the well bore and bonds the exterior surfaces of the pipestring to the walls of the well bore. The cement sheath prevents theunwanted migration of fluids between zones or formations penetrated bythe well bore.

Hydraulic cement compositions are also commonly used to plug lostcirculation and other undesirable fluid inflow and outflow zones inwells, to plug cracks and holes in pipe strings cemented therein and toaccomplish other required remedial well operations.

After the cement is placed within the well bore a period of time isneeded for the cement to cure and obtain enough mechanical strength fordrilling operations to resume. This down time is often referred to as“waiting-on-cement.” If operations are resumed prior to the cementobtaining sufficient mechanical strength, the structural integrity ofthe cement can be compromised.

In carrying out primary cementing as well as remedial cementingoperations in well bores, the cement compositions are often subjected tohigh temperatures, particularly when the cementing is carried out indeep subterranean zones. These high temperatures can shorten thethickening times of the cement compositions, meaning the setting of thecement takes place before the cement is adequately pumped into theannular space. Therefore, the use of set retarding additives in thecement compositions has been required. These additives extend thesetting times of the compositions so that adequate pumping time isprovided in which to place the cement into the desired location.

A variety of cement set retarding additives have been developed and areutilized in oil well cementing, such as sugars or sugar acids. Hydroxycarboxylic acids, such as tartaric acid, gluconic acid and glucoheptonicacid are also commonly used in oil well cementing as retarders. However,if an excess amount of retarder is used it can over-retard the set ofthe cement slurry, thereby causing it to remain fluid for an extendedperiod of time. This over-retardation can result in an extendedwaiting-on-cement time and cause delays in subsequent drilling orcompletion activities.

In a number of cementing applications, aqueous salts have been utilizedas an additive in cement compositions. Certain salts, such as calciumsalts, can act as accelerating agents, which reduce the setting time ofthe cement composition in an attempt to overcome the negative effects ofset retarders. However, the presence of a set and strength acceleratingagent, such as calcium salt, in the cement composition can increase therisk that the cement composition may thicken or set before placement.

Given the complexity of the cement chemistry and the large temperatureand pressure gradients present in the well bore, and the difficulty inpredicting the exact downhole temperatures during the placement andsetting of the cement, it can be difficult to control the retardingadditive and accelerating agent to get the desired setting behavior.There is a need for improved set control methods, which bring aboutpredictable cement composition setting times in the subterraneanenvironments encountered in wells. In particular, it is desirable todevelop methods for rapidly setting cement-based systems whereby thetiming of the setting is under the control of technicians in the fieldwithout the risk of premature setting. Therefore, a cement that can bemade to set on demand within the well bore is desirable. Such cementcompositions could be useful, for example, when lost circulation zonesare encountered in the subterranean formation. Setting a cementcomposition on demand to seal off the leak to the lost circulation zonewould be desirable.

Other subterranean fluids can also benefit from the initiation of achemical reaction downhole on demand. For example, it may be desirableto have a fluid that comprises a polymer crosslink downhole to form apill to counteract lost circulation. The fluid could require lesshydrostatic pressure for pumping, and then crosslink downhole when andwhere desired to form a more viscous fluid that may prevent fluid loss.Other downhole fluids and chemicals may also benefit from the ability tobe activated on demand within a subterranean formation.

SUMMARY OF THE INVENTION

The present invention relates to subterranean treatment operations, andmore particularly, to providing controlled delivery of subterraneanfluid additives to a well bore treatment fluid and/or a surroundingsubterranean environment using intelligent materials that respond to amagnetic stimulus to release subterranean fluid additives downhole in asubterranean environment.

In one embodiment, the present invention provides a method of releasinga subterranean fluid additive in a subterranean formation comprising:providing a magnetically-sensitive component that comprises asubterranean fluid additive; providing a magnetic source; and releasingthe subterranean fluid additive in the subterranean formation from themagnetically-sensitive component using the magnetic source.

In one embodiment, the present invention provides a method comprising:using a magnetic source to release a subterranean fluid additive in asubterranean formation.

In one embodiment, the present invention provides a method of cementingcomprising: providing a cement composition that comprises amagnetically-sensitive component; providing a magnetic source; releasinga cement activator from the magnetically-sensitive component using themagnetic source; and allowing the cement composition to set.

In one embodiment, the present invention provides a well borecomposition comprising: a well bore treatment fluid; and amagnetically-sensitive component that comprises a subterranean fluidadditive.

The features and advantages of the present invention will be readilyapparent to those skilled in the art upon a reading of the descriptionof the preferred embodiments that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of thepresent invention, and should not be viewed as exclusive embodiments.

FIG. 1 illustrates an example of an embodiment of an example of amagnetically controlled device.

FIG. 2 represents a theoretical example of the effect of magnetic forceon a ferrogel and the subterranean fluid additive release mechanism.

FIG. 3 represents a theoretical example of a ferrogel release of asubterranean fluid additive.

DETAILED DESCRIPTION

The present invention relates to subterranean treatment operations, andmore particularly, to providing controlled delivery of subterraneanfluid additives to a well bore treatment fluid and/or a surroundingsubterranean environment using intelligent materials that respond to amagnetic stimulus to release subterranean fluid additives downhole in asubterranean environment.

Of the many advantages of the present invention, only a few of which arediscussed or alluded to herein, the present invention provides for theuse of novel intelligent materials for the magnetically controlledrelease of subterranean fluid additives to a well treatment fluidlocated downhole in a subterranean formation. The intelligent releasematerials of the present invention respond to the use of magnetic forcesfrom a magnetic source to effect the release of subterranean fluidadditives. The term “magnetic source” as used herein refers to amaterial or object that produces a magnetic force. This magnetic forceis invisible, but is responsible for the most notable property of amagnet: a force that pulls on other ferromagnetic materials like ironand attracts or repels other magnets. Magnetic stimulation for releaseof the subterranean fluid additive is desirable because magneticstimulation is an action-at-a-distance force (i.e., a non-contactforce). The novel intelligent materials adaptively change their physicalprofiles due to the application of an external magnetic force, resultingin release of the contained subterranean fluid additives. This releasemay be advantageously employed in downhole applications to affect animmediate change in a fluid, for example, a cement composition, a gelledfluid, or a consolidating agent.

For instance, if the subterranean fluid additive is a cement activator,upon release, the activator can interact with a cement slurry in thedownhole environment to provide setting of the cement slurry on demandin a desired location within a well bore or a subterranean formation.This may be useful to activate hydration of a cement compositiondownhole. In certain embodiments of the present invention, the releaseof the magnetically-sensitive component can result in a “flash-set” ofat least a portion of the cement composition. As referred to herein, theteen “flash-set” will be understood to mean the irreversible setting ofat least a portion of the cement composition within a time in the rangeof from about 1 minute to about 5 minutes after contacting the cementcomposition with an activator that is released from themagnetically-sensitive component.

Similarly, if the subterranean fluid additive is a crosslinking agent,the crosslinking agent can interact with polymers in a well boretreatment fluid that comprises crosslinkable polymer located downhole soas to crosslink those polymers to create a viscous pill or plug that canprevent fluid leak-off into the surrounding formation. This may bedesirable, for example, to facilitate the formation of a gelled pill toprevent fluid loss into an area in a subterranean formation where athief zone or a lost circulation zone is present. In counteractinglost-circulation problems, a lost-circulation pill prepared inaccordance with the present invention may be designed to plug theperforations or formation interval losing the fluid. The viscous pillalso may be useful to perform a sweep around the well bore to pick updebris or well bore fill.

An additional application is where the subterranean fluid additive is acuring agent for a consolidating agent polymer located downhole. Suchapplications may be useful for activating consolidating agents such ascurable resins and tackifiers that may be used downhole to combatparticulate migration. The curing agent may interact with theconsolidating agent polymer so as to activate the polymer to enable itto consolidate particulates downhole to prevent their migration to thewell bore. Curing or activating the consolidating agent polymerson-demand with a curing agent of the present invention may preventpremature curing of the polymer, which is undesirable.

Other subterranean applications for which it may be desirable to containsubterranean fluid additives until a desired reaction time may alsobenefit from the intelligent materials and methods of the presentinvention.

The term “well bore treatment fluid” as used herein refers to a fluidthat is present in a subterranean formation. The subterranean formationmay comprise a well bore penetrating that subterranean formation. Theterm “in a subterranean formation” and its derivatives as used hereindoes not imply any particular location in the formation other than beingsubsurface.

In some embodiments, the magnetically-sensitive component is amechanically activated device, a ferrogel, or combination thereof thatcontains a subterranean fluid additive for release. Each of these willbe discussed below.

Suitable mechanically activated devices are those that are activated bya magnetic force to cause a mechanical release of a subterranean fluidadditive therefrom. An example of a mechanically activated device is aremotely controlled device that is activated by a magnetic forcegenerated from a magnetic source so as to release a contained orenclosed subterranean fluid additive downhole. By repeating the on-offoperation of the magnetic force, a controllable release of thesubterranean fluid additive from the mechanically activated device canbe programmably designed. In an embodiment, a system includes aremotely, magnetically controlled device and an associated controller.

FIG. 1 illustrates an embodiment of an example of a magneticallyactivated device. This is merely an example, and should not be read toincorporate all embodiments of suitable magnetically activated devices.Shown in FIG. 1 is a body structure 102 adapted for positioning in asubterranean formation, a reaction region 104 located in the bodystructure, the reaction region incorporating a first subterranean fluidadditive 106 (shown after release), and a remotely magneticallyactivatable control element 108 operably connected to the body structureand responsive to a magnetic force to release at least a portion of thesubterranean fluid additive 106 from the device. Optionally, an internalspace 110 may be located within the device. An embodiment may include aremote control signal source capable of generating an electromagneticcontrol signal sufficient to activate the remotely activatable controlelement to release a portion of the subterranean fluid additive 106. Insome embodiments, the reaction region 104 may be in fluid communicationwith the surrounding environment, via an inlet 112 and/or an outlet 114,as shown in FIG. 1.

As used herein, the term “remote” refers to the transmission ofinformation (e.g., data or control signals) or power signals or otherinteractions between the remote controller or the reaction systemwithout a connecting element such as a wire or cable linking the remotecontroller and the reaction system, and does not imply a particularspatial relationship between the remote controller and the reactiondevice, which may, in various embodiments, be separated by relativelylarge distances (e.g., greater than about a meter) or relatively smalldistances (e.g., less than about a meter). In addition, remote controlof the magnetically-sensitive component may be accomplished through theuse of a wireless network system, for example, as that taught in U.S.Pat. No. 6,985,750, the entirety of which is hereby incorporated byreference.

According to various embodiments, a mechanically activated device isplaced in an environment in order to initiate a chemical reaction inthat environment. Exemplary environments include a subterraneanformation, for example, to activate a cement composition, crosslink apolymer, or cure a consolidating agent.

Suitable mechanically activated devices may be placed downhole, forexample, in a fluid or via a wireline or other suitable carrier. Thestructure of the device may be adapted for a specific environment. Thesize, shape, and materials of the structure influence suitability for aparticular environment. For use in a subterranean environment, thedevice may be designed to withstand environmental conditions such astemperature, pressure, chemical exposure, erosion, abrasion, and othermechanical stresses. Moreover, the device may include features thatallow it to be placed or positioned in a desired location in thesubterranean formation, or targeted to a desired location in thesubterranean formation. Such features may include size and shapefeatures, tethers, or gripping structures to prevent movement of thedevice in the environment (in the case that the device is placed in thedesired location) or targeting features (surface chemistry, shape, etc.)that may direct the device toward or cause it to be localized in adesired location in the subterranean formation.

Small devices may be constructed using methods known to those havingordinary skill in the art of microfabrication or nanofabrication. Inapplications where size is not a constraint, a wide variety offabrication methods may be employed.

In some embodiments, a mechanically activated device may be formedentirely of a magnetically or an electrically responsive material orstructure. In other embodiments, a mechanically activated device mayinclude multiple magnetically responsive components (e.g., ferrousparticles). For example, the mechanically activated devices may compriseferrous materials, magnetite (Fe₃O₄), maghemite (Fe₂O₃), iron oxidenanoparticles, and combinations thereof, so as to respond to a magneticforce.

In selected embodiments, a magnetic field, an electric field, orelectromagnetic control signal may be used to activate the mechanicallyactivated device. The response of the mechanically activated device mayinclude, but is not limited to, one or more of: heating, cooling,vibrating, expanding, stretching, unfolding, contracting, deforming,softening, or folding. The mechanically activated device may includevarious materials, such as polymers, ceramics, plastics, dielectrics ormetals, or combinations thereof. The mechanically activated device mayinclude a shape memory material such as a shape memory polymer or ashape memory metal, or a composite structure such as a bimetallicstructure. The mechanically activated device may include a magneticallyor electrically active material. Examples of magnetically activematerials include permanently magnetizable materials, ferromagneticmaterials such as iron, nickel, cobalt, and alloys thereof,ferrimagnetic materials such as magnetite, ferrous materials, ferricmaterials, diamagnetic materials such as quartz, paramagnetic materialssuch as silicate or sulfide, and antiferromagnetic materials such ascanted antiferromagnetic materials which behave similarly toferromagnetic materials; examples of electrically active materialsinclude ferroelectrics, piezoelectrics and dielectrics. In someembodiments, the remotely activatable control element may include aferrogel.

Suitable examples of mechanically activated devices that might beadapted for use in subterranean applications for the release ofsubterranean fluid additives are described herein in U.S. PatentApplication Publication No. 2007/0106331, the entirety of which ishereby incorporated by reference.

In some embodiments, the magnetically-sensitive component is amagnetically controlled ferrogel comprising a subterranean fluidadditive, whereby an external magnetic field can be used to control therelease of the subterranean fluid additive from the ferrogel to thesurrounding environment, for example, a well treatment fluid forinitiating a desired result. The term “ferrogel” as used herein refersto a magnetically-sensitive polymer gel. The three-dimensional networkstructure of a ferrogel is believed to be formed fromhydrogen-bond-bridges or polymer microcrystals within the gel structure.Magnetically-sensitive hydrogels can undergo quick, relativelycontrollable changes in shape when subjected to magnetic force becauseof the presence of the magnetic particles within the gel particles. Whensubjected to a magnetic force, the magnetic particles align so as tochange the shape and/or internal molecular configuration of theferrogel, releasing at least some of the subterranean fluid additivefrom the ferrogel into the desired well treatment fluid or area of asubterranean formation. In an embodiment, a ferrogel that may be usedcomprises a subterranean fluid additive, a polymer matrix, and magneticparticles.

While not wishing to be limited by any particular theory as to how theferrogels function to release the subterranean fluid additive, FIG. 2shows a possible release mechanism of the subterranean fluid additivefrom the ferrogel when subjected to magnetic force. As shown in 202,when there is no magnetic force, the magnetic particles are randomlyoriented within the polymer matrix, and the diffusion mechanism is basedon the diffusion of the subterranean fluid additive through the polymermatrix. This diffusion may be related to the dissolution of the polymermatrix under downhole conditions, and the inherent diffusion rate of thesubterranean fluid additive within the polymer matrix. When a magneticapplied, the magnetic moments of the magnetic particles align, generallyalong the magnetic fields, and are thought to produce a bulk magneticmoment. This is thought to induce the Fe₃O₄ particles within theferrogel to aggregate together instantly, leading to a rapid decrease inthe porosity of the ferrogel leading to a “closed configuration” asshown in 204. This closed configuration may reduce the inherentdiffusion rate of the subterranean fluid additive from the ferrogel byconfining the subterranean fluid additive within the network of theferrogel. The closed configuration may also exhibit a decreased swellingratio. When the magnetic force is removed, as shown in 206, the closedpores reopen allowing the subterranean fluid additive to move to thesurfaces of the ferrogel, resulting in a burst release of thesubterranean fluid additive. After the burst release, it is believedthat the diffusion rate of the subterranean fluid additive from theferrogel may be reduced to a normal diffusion profile. By repeating theon-off operation of the magnetic field, a controllable release of thesubterranean fluid additive from the ferrogel can be programmablydesigned. The time spent switching between the on and off position ofthe magnetic force can control the release profile of the subterraneanfluid additive.

FIG. 3 illustrates another hypothetical release mechanism for theferrogels. In FIG. 3, a schematic drawing of a ferrogel structure showsiron oxide particles 302, a polymer matrix 304, and subterranean fluidadditive molecules 306. When a high frequency magnetic field is applied,the iron oxide particles 302 provide heat energy 308 to release thestructures and twist and shake the polymer matrix to effectivelyaccelerate release of the subterranean fluid additive 306. The burstingrelease of the subterranean fluid additive from the ferrogel isindicative of a mixture of mechanical actions imposed by the ferrogels,which may include, but are not limited to, (1) an “open” configurationof the network structure, and (2) an elastic deformation (i.e.,contractile deformation) of the ferrogels, while being subject instantlyto the high frequency magnetic field stimulus. Under high frequencymagnetic force, the nanomagnets are activated kinetically and possiblythermally (for larger nanoparticles), and they transform the structuralor molecular configurations of the ferrogels upon microstructuraldeformation (shrinking) of the polymer matrix.

Suitable polymers for use in the polymer matrixes of the ferrogelsinclude, but are not limited to, poly(vinyl alcohol) (“PVA”), chitosan,gelatin, dextran, sodium polyacrylate, and acrylate polymers, andcopolymers with an abundance of hydrophilic groups. PVA may beespecially suitable because it displays amphoteric characteristics andcan be applied in aqueous environments as well as in organic solventsfor the encapsulation of subterranean fluid additives. Moreover, PVA mayact as a sort of dispersing agent within the ferrogels to more uniformlydisperse the magnetic particles therein.

Suitable magnetic particles include, but are not limited to, particlesthat may be incorporated within a ferrogel so as to allow the ferrogelto respond to a magnetic force so as to release a subterranean fluidadditive from the ferrogel to a desired well bore treatment fluid orsubterranean environment. Such particles commonly consist of magneticelements such as iron, nickel and cobalt and their chemical compounds.Specific examples include, but are not limited to, ferrous materials,magnetite (Fe₃O₄), maghemite (Fe₂O₃), iron oxide nanoparticles, andcombinations thereof. In an embodiment, the particles are sized to bepresent in an adequate concentration within the ferrogel to allow theferrogel to respond to the magnetic force while also allowing for asufficient concentration of the subterranean fluid additive to bepresent therein.

In some embodiments, the magnetic particles are nano-sized ormicro-sized. If nanoparticles are used, suitable sizes for the magneticparticles may be, for example, (1) larger diameter (150-500 nm), (2)medium diameter (40-60 nm), or smaller diameter (5-10 nm). However, itis understood that the magnetic particles may comprise any suitable sizeor range of sizes within the range of from about 1 nm to about 1 μm. Insome embodiments, the magnetic particles may be larger than about 1 μm.The magnetic particles may be fabricated from an in situ coprecipitationprocess. The size of the magnetic particles may affect the quantity andrelease profile of the subterranean fluid additive.

To determine the concentration of the subterranean fluid additive in aferrogel for use in the methods of the present invention, a controlledrelease model may be developed. A release model may be realized with apredetermined release amount of the subterranean fluid additive, eitheras a membrane or a bulk structural configuration, via internally orexternally magnetically triggered operations. In general, enoughsubterranean fluid additive should be used to provide the necessaryaction downhole relative to the treatment fluid. Considerations include,but are not limited to, the inherent diffusion rate as well as the burstrelease concentration and any subsequent diffusion of the subterraneanfluid additive. Particle size and microstructural variations in theferrogels may affect their release profile.

The magnetic-sensitive behaviors in the ferrogels may be furtherexpressed by the difference in the permeated subterranean fluid additiveamount between the magnetic force in an “off” mode and in an “on” mode.The magnetic force can be alternately switched on and off cyclicallyduring a single operation to achieve a desired release rate and profile.The time period between the on and off modes may be referred to as aswitching duration. The length of the switching duration may affect therelease of the subterranean fluid additive from the ferrogels. Cyclicrelease rates may allow the subterranean fluid additive to reach akinetically favorable distribution in the ferrogel for a subsequentburst release.

Some ferrogels that can be adapted for use in subterranean applicationsfor the release of subterranean fluid additives are described herein inU.S. Patent Application Publication Nos. 2009/0258073 and 2007/0106331,the entirety of each is hereby incorporated by reference. Otherreferences that describe ferrogels include the following: Hu, et al.,“Controlled Pulsatile Drug Release from a Ferrogel by a High-FrequencyMagnetic Field,” Macromolecules 2007, 40, 6786-6788; Filipcsei, et al.,“Magnetic Field-Responsive Smart Polymer Composites,” Adv. Polymer Sci.(2007) 206: 137-189; and Lui, et al., “Magnetic-Sensitive Behavior ofIntelligent Ferrogels for Controlled Release of Drug,” Langmuir (2006),22, 5974-5978, the entirety of each is hereby incorporated by reference.Suitable subterranean fluid additives for use in the present inventioninclude, but are not limited to, additives that are useful in downholeoperations for causing a rapid reaction in the context of a treatmentfluid. Examples include, but are not limited to, cement activators,crosslinking agents, and curing agents for curable consolidating agents.The term “subterranean fluid additive” as used herein refers to asubterranean fluid additive that has utility in subterraneanapplications.

Examples of suitable cement activators include, but are not limited to,sodium hydroxide, sodium carbonate, an amine compound, calcium, sodium,magnesium, aluminum, calcium chloride, sodium chloride, sodiumaluminate, magnesium chloride, sodium silicate, or any combinationthereof. An example of a suitable calcium salt is calcium chloride.Examples of suitable sodium salts are sodium chloride, sodium aluminate,and sodium silicate. An example of a suitable magnesium salt ismagnesium chloride. Other activators may include seawater and thoseknown in the art. The choice of a proper cement activator will be madein consideration for the chemical composition of the cement compositionbeing set.

In certain embodiments of the present invention wherein the cementcomposition is intended to flash-set, activators that may beparticularly suitable may include, inter alia, sodium hydroxide, sodiumcarbonate, potassium carbonate, bicarbonate salts of sodium orpotassium, sodium silicate salts, sodium aluminate salts, ferrous andferric salts (e.g., ferric chloride and ferric sulfate), polyacrylicacid salts, and the like. In certain embodiments of the presentinvention, activators such as calcium nitrate, calcium acetate, calciumchloride, and calcium nitrite may be used to cause the cementcomposition to flash-set, though the concentration of these activatorsthat may be required in order to cause such flash-setting may be greaterthan the concentration required for the other activators describedherein, and their equivalents. One of ordinary skill in the art, withthe benefit of this disclosure, will be able to identify an activatorconcentration sufficient to cause flash-setting of a cement composition.

The amount of activator generally required is an amount that issufficient to cause the cement composition to set within a time in therange of from about 1 minute to about 2 hours after contacting theactivator. In certain embodiments wherein the activator is sodiumchloride, the desired effective concentration may be in the range offrom about 3% to about 15% by weight of the water in the cementcomposition. In certain embodiments wherein the activator is calciumchloride, the desired effective concentration may be in the range offrom about 0.5% to about 5% by weight of the water in the cementcomposition.

Although the compositions and methods of the present invention may beuseful in conjunction with any cement composition that is used in asubterranean application, examples of cement compositions that may beused in conjunction with the present invention include hydraulic cementcompositions. These are typically used in the form of an aqueous slurryof hydraulic cement with a concentration of retarder mixed in theaqueous slurry to control or delay the cement setting time so that itexceeds the pumping time with an adequate safety margin. Sufficientwater is added to the slurry to make the composition pumpable. Suchhydraulic cements, include, but are not limited to, Portland cements,pozzolana cements, gypsum cements, high-alumina-content cements, slagcements, silica cements, and combinations thereof. In certainembodiments, the hydraulic cement may comprise a Portland cement. ThePortland cements that may be suited for use in exemplary embodiments ofthe present invention are classified as Class A, C, H and G cementsaccording to American Petroleum Institute, Recommended Practice forTesting Well Cements, API Specification 10B-2 (ISO 10426-2), Firstedition, July 2005.

Other additives suitable for use in subterranean cementing operationsalso may be added to embodiments of the cement compositions, inaccordance with embodiments of the present invention. Examples of suchadditives include, but are not limited to, strength-retrogressionadditives, set accelerators, set retarders, weighting agents,lightweight additives, gas-generating additives, mechanical propertyenhancing additives, lost-circulation materials, filtration-controladditives, a fluid loss control additive, dispersants, defoaming agents,foaming agents, thixotropic additives, and combinations thereof. By wayof example, the cement composition may be a foamed cement compositionfurther comprising a foaming agent and a gas. Specific examples ofthese, and other, additives include crystalline silica, amorphoussilica, fumed silica, salts, fibers, hydratable clays, calcined shale,vitrified shale, microspheres, fly ash, slag, diatomaceous earth,metakaolin, rice husk ash, natural pozzolan, pumicite, perolite,zeolite, cement kiln dust, lime, elastomers, resins, latex, combinationsthereof, and the like. A person having ordinary skill in the art, withthe benefit of this disclosure, will readily be able to determine thetype and amount of additive useful for a particular application anddesired result.

Another subterranean fluid additive that may be useful in the presentinvention is a crosslinking agent that when released, crosslinks agelled fluid downhole so as to increase its viscosity to form a pill.This “pill” can be useful to control fluid loss or prevent furtherleak-off into a particular area in a formation. The pill may have atraditional pill form, or it may form a type of plug. These gelledfluids may be aqueous-based fluids that comprise a gelling agent, whichmay be crosslinked. These gelling agents may be biopolymers or syntheticpolymers. Common biopolymer gelling agents include, e.g., galactomannangums, cellulosic polymers, and other polysaccharides. Because of theircost and effectiveness, biopolymers are most commonly used. However, inhigh temperature applications, these gelling agents can degrade, whichcan cause the viscosified treatment fluid to prematurely lose viscosity.Various synthetic polymer gelling agents have been developed for use inviscosified treatment fluids. The choice of a particular crosslinkingagent to include will depend on the gelling agent polymer present in thegelled fluid downhole. Suitable crosslinking agents may includeboron-based crosslinking agents, zirconium-based crosslinking agents andtitanium-based crosslinking agents. Hafnium-based crosslinking agentsalso may be suitable. Zirconium-based commercially availablecrosslinking agents suitable for use in this invention include thoseavailable under the trade names “CL-23” and “CL-24,” which are bothavailable from Halliburton in Duncan, Okla.

In certain embodiments, the crosslinking agent may be included in amagnetically-sensitive component in an amount in the range of from about0.02% to about 1.2% by volume of the aqueous base fluid, more preferablyin the amount of about 0.5%.

Another subterranean fluid additive that may be suitable for use in thepresent invention is a curing agent (also known as a polymerizationinitiator) for a consolidating agent downhole to control, for example,particulate migration downhole. Sand consolidation is a near well boretreatment of a well to be tested or placed in production. Surrounding awell bore in many instances are incompetent highly porous andfragmentable sand or particulate formations. Under productionconditions, the particulate is often displaced from its aggregatedstructure and carried along by a fluid flowing to a producing well. Ifthe particulate flow is allowed to proceed unchecked the producing wellbore soon becomes full of sand, thereby clogging oil production.Furthermore, particulate arriving at the surface of the well can causewear to the production hardware.

Suitable consolidating agents comprise curable resins; tackifyingagents; or a getable liquid compositions. Examples of curable resinsthat can be used in the present invention include, but are not limitedto, organic resins such as polyepoxide resins (e.g., bisphenolA-epichlorihydrin resins), polyester resins, urea-aldehyde resins, furanresins, urethane resins, and mixtures thereof. Some suitable resins,such as epoxy resins, may be cured with an internal catalyst oractivator so that when pumped down hole, they may be cured using onlytime and temperature. Other suitable resins, such as furan resinsgenerally require a time-delayed catalyst or an external catalyst tohelp activate the polymerization of the resins if the cure temperatureis low (i.e., less than 250° F.), but will cure under the effect of timeand temperature if the formation temperature is above about 250° F.,preferably above about 300° F.

Generally, a curing agent used is included in an amount in the range offrom about 5% to about 75% by weight of the curable resin. In someembodiments of the present invention, the resin curing agent used isincluded in the curable resin composition in an amount in the range offrom about 20% to about 75% by weight of the curable resin.

The magnetic force used to activate the release mechanism of themagnetically-sensitive components described herein may be generated fromany suitable magnetic source.

In some embodiments, the magnetic force is generated from anelectromagnetic, for example, an electromagnet that is placed on awireline and run downhole through casing. The electromagnet may also bepulled up through the casing. The magnetic force may also be generatedfrom a more permanent magnet located on the casing or a portion of thecement shoe. In such embodiments, it may be possible to pump a cementcomposition past the downhole magnetic source near the casing or shoe sothat the cement is then activated. The activated cement composition canthen be pumped further to its desired location and allowed to set. Insuch embodiments, the additional pumping time after activation is takeninto account so that the cement composition does not prematurely setbefore desired placement. In other embodiments, the magnetic source maybe located at the well site above-ground. In such instances, theactivated species may be activated on-the-fly and pumped downhole.

In some embodiments, the magnetic force may be generated by applying acurrent to an electromagnetic coil. In other embodiments, the magneticforce may be applied by a magnetic circuit.

Other examples of tools that contain magnetic sources that may be usedto activate the release mechanism of the magnetically-sensitivecomponents include, but are not limited to, MRI tools, solenoidactuators, and magnetic couplings. Examples of such downhole tools mayinclude, but are not limited to, subterranean logging devices, flowmeters, formation evaluation tools, directional drilling equipment,directional or other survey instruments, coils, gyroscopic apparatus,MRI tools, photo-multipliers, casing or tubing collar locators,information gathering and/or transmitting devices and various electricaltools.

In some embodiments, the source of the magnetic force may be locatedwithin a plug that is pumped down a casing, for example, a cementingplug. In this example, as the cementing plug proceeds downhole, themagnetic force activates the cement slurry by releasing a cementactivator from a magnetically-sensitive component located downhole.

In some embodiments, the present invention provides a method comprising:using a magnetic force to release a subterranean fluid additivedownhole.

In some embodiments, the present invention provides a method ofreleasing a subterranean fluid additive in a subterranean formationcomprising: providing a magnetic source and a magnetically-sensitivecomponent that comprises a subterranean fluid additive; and releasingthe subterranean fluid additive in the subterranean formation from themagnetically-sensitive component using a magnetic force generated fromthe magnetic source.

In some embodiments, the present invention provides a method comprising:placing a magnetic source in a well bore penetrating a subterraneanformation; and releasing a subterranean fluid additive in thesubterranean formation from a magnetically-sensitive component using amagnetic force generated from the magnetic source.

In some embodiments, the present invention provides a method comprising:placing a ferrogel in a subterranean formation.

In some embodiments, the present invention provides a method comprising:placing a remotely, magnetically controlled device and an associatedcontroller in a subterranean formation.

In some embodiments, the present invention provides well bore treatmentfluids that include a ferrogel comprising a well bore subterranean fluidadditive, a polymer matrix, and a magnetic species.

In some embodiments, the present invention provides well bore treatmentfluids that include a magnetically-sensitive component comprising asubterranean fluid additive.

In some embodiments, the present invention provides a method ofcementing in a subterranean formation: introducing a cement compositioninto the subterranean formation, wherein the cement compositioncomprises cement, a retarder, and water; providing a magnetic source anda magnetically-sensitive component that comprises a subterranean fluidadditive; introducing the magnetically-sensitive component into thesubterranean formation; releasing the subterranean fluid additive fromthe magnetically-sensitive component using a magnetic force generatedfrom the magnetic source, wherein the subterranean fluid additiveactivates hydration of the cement; and allowing the cement compositionto set in the subterranean formation. In some embodiments, the cementcomposition is placed in an annulus between casing and the subterraneanformation, and is allowed to set therein.

In some embodiments, the present invention provides a method of forminga crosslinked pill in a subterranean formation: introducing a fluidcomprising a crosslinkable polymer into the subterranean formation;providing a magnetic source and a magnetically-sensitive component thatcomprises a subterranean fluid additive; introducing themagnetically-sensitive component into the subterranean formation;releasing the subterranean fluid additive from themagnetically-sensitive component using a magnetic force generated fromthe magnetic source, wherein the subterranean fluid additive activatescrosslinking of the polymer; and allowing a crosslinked pill to form.

In some embodiments, the present invention provides a method ofconsolidating particulates in a subterranean formation: introducing afluid comprising a curable consolidating agent into the subterraneanformation; providing a magnetic source and a magnetically-sensitivecomponent that comprises a subterranean fluid additive that comprises acuring agent; introducing the magnetically-sensitive component into thesubterranean formation; releasing the subterranean fluid additive fromthe magnetically-sensitive component using a magnetic force generatedfrom the magnetic source; and allowing the consolidating agent to cure.

In some embodiments, the present invention provides a method ofcalculating the diffusion of a subterranean fluid additive from aferrogel using a diffusion coefficient corresponding to the diffusionand release rate of the subterranean fluid additive from the ferrogelinto a fluid located in a subterranean formation.

To facilitate a better understanding of the present invention, thefollowing examples of preferred embodiments are given. In no way shouldthe following examples be read to limit, or to define, the scope of theinvention.

EXAMPLES

A suitable ferrogel for use in the present invention may be preparedaccording to the following prophetic method involving a freezing-thawingtechnique.

First, 5 wt % PVA with a molecular weight of about 72,000, and a degreeof hydrolyzation of about 97.5% to about 99.5% is dissolved in 10 ml ofdimethyl sulfoxide (“DMSO”) at 80° C. under stirring for 6 hours andthen mixed with 17 wt % of magnetic particles at 60° C. underultrasonication for 6 h to ensure that the magnetic particles are welldispersed. The resulting solution is then poured into a plastic dish andfrozen at −20° C. for 16 h. Subsequently, the gels are then thawed at25° C. for 5 h. This cyclic process including freezing and thawing isrepeated 5 times. The resulting ferrogels are then washed to removedDMSO. This is done by washing the ferrogels 5 times and then immersingthem in water for 24 h. The ferrogels can be stored at 4° C. until theyare used or tested.

The diffusion coefficients for the ferrogels may be measured using thisprophetic procedure. The diffusion coefficients can be measured using aswitching magnetic force (400 Oe) in a diffusion diaphragm cell (aside-by-side cell). The solution in the donor side is a 80 ml of anisotonic phosphate buffer (“PBS”) (pH of 7.4) containing 200 ppm of thesubterranean fluid additive. The receptor compartment, separated by theferrogel, is tilled with 80 ml of PBS solution. The concentration ofeach compound in the receptor compartment can be determined to by λ=361nm using a UV spectrophotometer. The diffusion coefficient can becalculated according to the following equation for the diaphragm cell:

In(C _(d0)/(C _(d) −C _(r)))=2PAt/δ V  Equation 1

Where C_(d0) is the initial concentration of the permeant in the donorcompartment; C_(d) and C_(r) are indicative of the concentrations in thedonor side and the receptor side, respectively; P is the permeabilitycoefficient (cm2/min); A is the effective area of the ferrogel; δ is thethickness of the ferrogel; V are respectively the volumes of solution inthe donor and receptor compartment (both are 80 ml above). By plottingln(C_(d0)/(C_(d)−C_(r))) versus time (t), the permeability coefficient(P) can be calculated from the slope of the line by Equation 1. Datapoints may be averaged to form the plot.

A prophetic cementing example of the present invention includesproviding a cementing composition that comprises a cement, water, aferrogel including a cement activator, and optionally a set retarder;and pumping the cement composition into the annulus of a well borelocated between the casing and the surrounding subterranean formation.Thereafter, at a desired time, a magnetic force is used to activate theferrogel, enabling a release of the activator to the cement compositionso that the cement composition is activated to set in a desired portionof the annulus.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered,combined, or modified and all such variations are considered within thescope and spirit of the present invention. While compositions andmethods are described in terms of “comprising,” “containing,” or“including” various components or steps, the compositions and methodscan also “consist essentially of” or “consist of” the various componentsand steps. All numbers and ranges disclosed above may vary by someamount. Whenever a numerical range with a lower limit and an upper limitis disclosed, any number and any included range falling within the rangeis specifically disclosed. In particular, every range of values (of theform, “from about a to about b,” or, equivalently, “from approximately ato b,” or, equivalently, “from approximately a-b”) disclosed herein isto be understood to set forth every number and range encompassed withinthe broader range of values. Also, the terms in the claims have theirplain, ordinary meaning unless otherwise explicitly and clearly definedby the patentee. Moreover, the indefinite articles “a” or “an”, as usedin the claims, are defined herein to mean one or more than one of theelement that it introduces. If there is any conflict in the usages of aword or term in this specification and one or more patent or otherdocuments that may be incorporated herein by reference, the definitionsthat are consistent with this specification should be adopted.

1-32. (canceled)
 33. A well bore composition comprising: a well boretreatment fluid; and a magnetically-sensitive component that comprises asubterranean fluid additive.
 34. The well bore composition of claim 33wherein the magnetically-sensitive component includes a magneticallyactivated device.
 35. The well bore composition of claim 33 wherein themagnetically-sensitive component is a ferrogel.
 36. The well borecomposition of claim 35 wherein the ferrogel comprises a polymer matrixand a magnetic species.
 37. The well bore composition of claim 33wherein the subterranean fluid additive comprises an additive selectedfrom the group consisting of a cement activator, a crosslinking agent,and a curing agent.
 38. The well bore composition of claim 33 whereinthe well bore treatment fluid is a cement composition.
 39. The well borecomposition of claim 33 wherein the well bore treatment fluid is a pill.40. The well bore composition of claim 33 wherein the well boretreatment fluid further comprises a consolidating agent.
 41. The wellbore composition of claim 34 wherein the magnetically activated deviceincludes a remote control signal source capable of generating anelectromagnetic control signal.
 42. The well bore composition of claim34 wherein the magnetically activated device is microfabricated.
 43. Thewell bore composition of claim 34 wherein the magnetically activateddevice is nanofabricated.
 44. The well bore composition of claim 34wherein the magnetically activated device comprises at least oneselected from the following: a polymer, a ceramic, a plastic, adielectric, metals, and any combination thereof.
 45. A well borecomposition comprising: a well bore treatment fluid; and a ferrogel thatcomprises a subterranean fluid additive.
 46. The well bore compositionof claim 45 wherein the ferrogel comprises a polymer selected from thegroup consisting of: poly(vinyl alcohol), chitosan, gelatin, dextran,sodium polyacrylate, an acrylate polymer, an acrylate copolymer, and anycombination thereof.
 47. The well bore composition of claim 45 whereinthe ferrogel comprises a magnetic particle selected from the groupconsisting of: an iron particle, a nickel particle, a cobalt particle, aferrous material, magnetite, maghemite, an iron oxide nanoparticle, andany combination thereof.
 48. The well bore composition of claim 45wherein the ferrogel comprises a magnetic particle having a size rangeof about 1 nm to about 1 μm.
 49. The well bore composition of claim 45wherein the well bore treatment fluid is a cement composition.
 50. Thewell bore composition of claim 49 wherein the ferrogel comprises acement activator selected from the group consisting of: sodiumhydroxide, sodium carbonate, an amine compound, calcium, sodium,magnesium, aluminum, calcium chloride, sodium chloride, sodiumaluminate, magnesium chloride, sodium silicate, and any combinationthereof.
 51. A well bore treatment fluid comprising a ferrogel thatcomprises a subterranean fluid additive, a polymer matrix, and amagnetic species.